Why do grocery store cashiers 'throw' my food?

Every time I go to the grocery store, be it national chain or local 'Mom and Pop,' I get steamed. The person checking me out will scan my products and with a flick of the wrist, toss my products onto the conveyor belt to the waiting bagger. The bagger will then drop my products into a bag. Whenever the checker scans eggs, I always tell them "Don't toss the eggs, they will break."

Do grocery stores actually teach this 'flick and toss' method? I am spending hard earned money for these items, and do not want my items tossed onto a conveyor belt! Especially if I have spent time picking produce only to have them bruised by the tossing and then dropping into bags.

Any checkers or baggers want to shed light on this? Is this part of the training?